Flare R is one of the best rear lights out there IMO. It's almost too bright for night time, though it does automatically change the light output depending on ambient light. The thing is a laser beam in daytime, I actually use a different light for night riding (Cateye Rapid X 2). Flare R is a very focused light, whereas the Cateye is more diffuse, which is better for night, when all I want is a blob of red light emanating from my bike. The focused beam of the Flare R is great for daytime riding, to pierce through bright sunlight. Both are USB.